The G-protein-coupled receptors (GPCR) form an important class of peptide-binding receptors. The various members of the GPCR family mediate a wide variety of intercellular signals.
Members of the GPCR family have seven helical domains which span the cell membrane and are linked by three extracellular loops and three intracellular loops. The receptors also posses an extracellular amino terminal tail and an intracellular carboxy terminal tail. The intracellular loops interact with a G-protein that can switch from a GDP-binding form to a GTP-binding form.
The binding of an appropriate ligand to a GPCR initiates the conversion of the coupled C-protein from its GDP-binding form to its GTP-binding form. This conversion, in turn, initiates a signal transduction cascade that generates a biological response. Depending on the nature of the GPCR, signal transduction activity can be measured by measuring the intracellular Ca2+ level, phospholipase C activation, the inositol triphosphate (IP3) level, the diacylglycerol level, or the adenosine cyclic 3xe2x80x2, 5xe2x80x2-monophosphate (AMP) level.
Marchese et al. (Genomics 29:335, 1995) describes the cloning and chromosomal mapping of GPR10, a human GPCR. Marchese et al. analyzed GPR10 expression in the brain and reported that no human GPR10 expression was observed in hypothalamus, putamen, pons, hippocampus, frontal cortex, thalamus, and cerebellum.
Welch et al. (Biochem. Biophys Res. Comm. 209:606, 1995) describes the cloning of UHR-1, a rat GPCR, from the hypothalamic suprachiasmatic nucleic, the circadian pacemaker of the human brain. According to Welch et al., UHR-1 has sequence similarity at the amino acid level to the receptors for the tachykinins, substance P, and substance K; the somatostatin receptors SSTR5 and SSTR3; the neuropepticle Y1 receptor; the delta, kappa, and mu opioid receptors, and the gastrin-CCK-B receptor. According to Welch et al., rat UHR-1 is expressed in rat pituitary, cerebellum, hypothalamus, pons, and hippocampus. No expression is present in rat neonatal brain, adult rat liver, lung, pancreas, kidney, spleen, small intestine, adrenal gland, testes, thymus, aorta, heart, skeletal muscle, or diaphragm.
Duhl (PCT Publication No. WO 97/08317) describes a protein referred to as xe2x80x9chuman hypothalamic receptorxe2x80x9d or xe2x80x9chHRxe2x80x9d. According to Duhl, hHR is a seven-transmembrane receptor. Duhl suggests that hHR can be used to identify agonists and antagonists of hHR activity.
Hinuma et al. (EP 0 845 529 A2) discloses two forms of a G-protein coupled receptor protein. Hinuma et al. report that one of the two forms of the disclosed G protein coupled receptor is expressed in the brain.
Hinuma et al. (Nature 393-272, 1998) describes xe2x80x9cprolactin-releasing peptidexe2x80x9d (PrRP) a peptide which binds to hGR3, a receptor that is expressed in human pituitary and is, according to Hinuma et al., nearly identical to both GPR10 and the human homologue of rat UHR-1. Hinuma et al. report that PrRP stimulates release of prolactin from anterior pituitary cells of lactating rats in vitro. Hinuma et al. also report that expression of PrRP and its receptor appear to fluctuate in the medulla oblongata and pituitary during pregnancy and lactation, respectively, in rats. Based on these results, Hinuma et al. suggest that the levels of PrRP and its receptor are closely related to the regulation of reproductive processes.
The invention features assays for the identification of compounds useful for the modulation of body weight. Such compounds are useful for the treatment of obesity and cachexia. The methods of the invention involve cell-free and cell-based assays that identify compounds (modulators) which bind to and/or activate or inhibit the activity of GPR10, a G protein-coupled receptor, followed by an in vivo assay of the effect of the compound on feeding behavior, body weight, or metabolic rate. The invention also features compounds which bind to and/or activate or inhibit the activity of GPR10 as well as pharmaceutical compositions comprising such compounds.
In addition, the invention includes nucleic acid molecules comprising a nucleotide sequence encoding all or a portion of murine GPR10, polypeptides comprising all or a portion of murine GPR10, antibodies directed against murine GPR10, and animals harboring a murine GPR10 transgene (e.g., mice overexpressing murine GPR10).
The invention also features pharmaceuticals compositions comprising a compound identified using the screening methods of the invention as a well as methods for preparing such compositions by combining a such a compound and a pharmaceutically acceptable carrier. Also within the invention are pharmaceutical compositions comprising a compound identified using the screening assays of the invention packaged with instructions for use. For modulators that are antagonists of GPR10 activity or expression, the instructions specify use of the pharmaceutical composition for treatment of high body weight (e.g., for reduction of body weight). For modulators that are agonists of GPR10 activity or expression, the instructions would specify use of the pharmaceutical composition for treatment of low body weight (i.e., for increase of body weight).